Pressable or extrudable explosive formulations typically include high solids content, from about 89 percent to 99 percent, by weight. For instance, typical extrudable explosives contain from about 89 to 92 percent solids, by weight. A well known extrudable explosive, Composition C4 contains 91% RDX in a binder of polyisobutylene and a liquid plasticizer. Pressable explosives usually contain from 92 to 99 percent solids, by weight. LX-14 is a well known pressable explosive containing 95.5 wt. % HMX and 4.5 wt. % polyurethane resin. Explosive compositions having a solids content below 89 weight percent are generally in the realm of castable explosives.
Polymer precipitation is an important processing technique used to obtain ultra-high solids content pressable explosives. At its simplest, polymer precipitation involves dissolving the polymer in a solvent, adding the dry ingredients and stirring vigorously, then adding a nonsolvent (relative to the polymer and dry ingredients) to the system to cause precipitation of the polymer. Thus, polymer precipitation is used to uniformly coat the dry ingredients with the precipitated polymer. The coated particles are then pressed to high density and into the shape desired for the application selected.
Polymers that have been successfully used in the polymer precipitation process are typically solid at the processing temperature, with a weight average molecular weight greater than about 20,000. Although the actual molecular weight may vary somewhat from polymer to polymer depending on the specific relationship between molecular weight, mechanical properties, and viscosity. High molecular weight is important to efficient polymer precipitation and pressed formulation integrity. Inert polymers have been used because they function as described above and also provide some desensitization of the explosive.
In recent years, energetic polymers, such as PGN (polyglycidyl nitrate), poly-NMMO (nitratomethyl-methyloxetane), poly-BAMO (poly(bis(azidomethyl)oxetane)), poly-AMMO (poly(azidomethylmethyloxetane)), GAP (polyglycidyl azide), and copolymers thereof have been developed and evaluated as replacements of inert polymeric binders in cast propellant systems. Such polymers have also been used in cast explosive compositions and pyrotechnics. However, these energetic polymers are not commercially available in high molecular weights and are typically liquid at normal processing temperatures. Such free flowing liquid binders are generally not suitable in pressable explosives because of problems with growth and exudation.
The substitution of an inert polymer with an energetic polymer in a typical pressable explosive composition will result in higher detonation pressures (typically 20 katm increase) and detonation velocities (typically 100 m/s increase). Because of the ongoing search for very high performance pressable explosives for use in metal accelerating applications, it would be a major advancement in the art to provide high performance high solids pressable explosives prepared from energetic polymers.
Such high performance high solids pressable explosive compositions are disclosed and claimed herein.